The laboratory of in vitro marrow culture is concerned with normal granulopoiesis and granulopoietic regulation, as well as abnormal granulopoiesis in bone marrow disease states such as leukemia, and following chemotherapy in non-marrow neoplastic conditions. During the past year, the in vivo and in vitro effects of methotrexate and the rescue of methotrexate toxicity by citrovorum factor and nucleosides on murine myelopoiesis was examined. A human granulopoietic colony-stimulating factor intended for clinical trial in aplastic states was extensively assayed in vitro with human marrow. A limiting problem with the assay is an inability to quantify growth without relying on a human subjective factor deriving from visual counts. A macrotube photoelectric counter has been developed and this machine is being calibrated to values found by visual colony counts on mouse and human marrow. Future projects to study clinical marrow and peripheral blood assays in patients with ovarian carcinoma will continue and studies of the chemotherapeutic effects on granulopoiesis will be extended to include hyperthermia plus chemotherapeutic studies.